Increased neurohumoral stimulation resulting in excessive sodium avidity and extracellular volume overload are hallmark features of decompensated heart failure. Especially in case of concomitant renal dysfunction, the kidneys often fail to elicit effective natriuresis. While assessment of renal function is generally performed by measuring serum creatinine-a surrogate for glomerular filtration-, this only represents part of the nephron's function. Alterations in tubular sodium handling are at least equally important in the development of volume overload and congestion. Venous congestion and neurohumoral activation in advanced HF further promote renal sodium and water retention. Interestingly, early on, before clinical signs of heart failure are evident, intrinsic renal derangements already impair natriuresis. This clinical review discusses the importance of heart failure (HF) induced changes in different nephron segments. A better understanding of cardiorenal interactions which ultimately result in sodium avidity in HF might help to treat and prevent congestion in chronic and acute HF.